The 3rd Generation Partnership Project (3GPP) is a collaboration between groups of telecommunications associations, to make a globally applicable third generation mobile phone system specification within the scope of the International Mobile Telecommunications-2000 project of the International Telecommunication Union (ITU). 3GPP specifications are based on evolved Global System for Mobile Communications (GSM) specifications. 3GPP standardization encompasses Radio, Core Network and Service architecture. The general architecture of a third generation mobile communication system 10 and its evolutions is illustrated in FIG. 1. The core network is the central part of a mobile network that provides various services to customers who are connected by the access network. The user equipment 20 is a mobile terminal by which a subscriber can access services offered by an operator's core network. The Radio Access Network (RAN) is the part of the network that is responsible for the radio transmission and control of the radio connection. A Radio Network Subsystem (RNS) consists of one Radio Network Controller (RNC) 40 and one or several base stations (BS) 30. Further, the Radio Network Controller (RNC) 40 controls radio resources and radio connectivity within a set of cells, as well as controlling the base stations within the RNS. A cell covers a geographical area and the radio coverage in a cell is provided by the base station handling radio transmission and reception within one or more cells.
In the 3GPP release 99, the RNC controls resources and user mobility. Resource control in this framework refers to admission control, congestion control, channel switching i.e. roughly changing the data rate of a connection. Furthermore, a dedicated connection is carried over a dedicated channel (DCH), which is realized as a Dedicated Physical Control Channel (DPCCH) and a Dedicated Physical Data Channel (DPDCH).
In enhanced 3G standards such as UMTS Release 6 specifications for Enhanced Uplink (EUL), the trend is to decentralize decision making and in particular the control over the short term data rate of the user connection. The uplink data is then allocated to E-DCH (enhanced DCH), which is realized as a DPCCH, which is continuous, and a E-DPCCH for data control and a E-DPDCH for data. The latter two are only allocated when there is uplink data to send. Hence, the base station uplink scheduler determines which transport formats each user can use over E-DPDCH. The RNC is however still responsible for admission and congestion control.
In W-CDMA (Wideband Code Division Multiple Access) the dedicated channels are power-controlled. In the uplink, this means that the base station measures the received DPCCH signal quality, SIR, and compares the measurements to a desired signal quality, SIR target. If the SIR is less than or equal to the SIR target, the base station signals the transmitter power control command ‘up’ to the UE to make it increase the power by a predefined step. If the SIR is higher than the SIR target, the base station signals the transmission power control command ‘down’ to the UE to make it decrease the power by a predefined step. The SIR target is regularly updated by the RNC via the DCH frame protocol procedures known as outer loop power control (OLPC). For DCH, the OLPC adjustments of SIR target are based on the Cyclic Redundancy Check Indicator (CRCI) indicating whether a data block was correctly decoded or not. For E-DCH, the hybrid automatic repeat request (HARQ) receiver handles multiple transmissions of a data block, which means that it is instead the number of HARQ retransmissions that are of interest. The number of HARQ retransmissions is sent over the DCH frame protocol procedures as well together with the data blocks. The number of HARQ retransmissions is coded by four bits in a “number of HARQ retransmissions” field in the DCH frame protocol, wherein value 0-11 indicates the number of HARQ retransmissions, value 12 indicates 12 or more HARQ retransmissions and value 15 indicates that the number of HARQ retransmissions is unknown. When the RNC receives a correctly decoded data block together with the value indicating the number of retransmissions, the latter value is compared to value of a target number of retransmissions. If the number of retransmissions exceeds the target number of retransmissions, the OLPC increases SIR target by a predefined step A, and if the number of retransmissions is lower or equal to the target number of retransmissions the OLPC decreases the SIR target by a predefined step B. The steps A and B are directly proportional to a configurable step size, and related to a configurable probability that the number of retransmissions exceeds the target number of retransmissions.
Moreover, when the number of retransmissions reaches a predefined limit, the base station signals HARQ error to the RNC according to the DCH frame protocol. In that signaled frame, the value of the number of retransmissions when the HARQ error occurred should also be indicated.